Electrical connector and method of making the same



F.v J. SOWA May 1, 1951 ELECTRICAL CONNECTOR AND METHOD OF' MAKING THE SAME Filed Oct. 6, 1943 lNyENToR UBY* j ATTORN Patented May 1, 1951 UNITED STA-TES PATENT OF FICE ELECTRICAL CONNECTOR AND METHOD' OFV MAKING THESAME FrankJ. Sowa, Cranford, N.' Jl., assigner to Aircraft-Marine Products Ine., Elizabeth,.N.` J., a corporation of NewJersey Application-October 6, 1943, Serial N0.; 505,-087

`7 IClaims. l This invention relates to. electrical connectors for conductors, and more particularly to asolderless type of connector, anda method of attaching it to aconductor end.

With solderlessconnections, evenunder normal conditions of use, corrosion may creep into the. area of contactvbetween the connector andconductor andimpair the conductivity as: to resultV in voltage variations which though. relatively slight are still .much too. great to permit efficient. operationof many diierent types of instruments.

Where. even small changes in. resistance may be. significant.

It isaccordingly among theI .objects ofi my inventiont'o. provide asimple, sturdy and durablel f electrical connector. for solderlcss attachment, to! f theend of an insulatedconductor which. among 1 otherV things. effectively seals contact areas. of. the. conductor against the admission of Vair. and" moisture. It isa further. objectof my invention4 to provide a method ofvmaking an` electrical connector of the above-mentioned type in a simple and efficient manner amenable to mass production manufacture. Another object of my.

invention lies in the provision of' a method of the wire'-r and/orferrule before assembly, that it'. does not interfere with: goo-d. electrical` contact-` in the crimpedv area but actually can improve both theinitial contact established'by the crimping and the stabilityV ofcontactresistance' during' long use.

The invention accordingly consists inthe-.feattures of' construction, combinations of elements,

arrangements of parts; and in theseveral steps` and relation and order of." each of the same. to

onel or more ofthe others; all as will he-` illustratively` described herein, and' the scope offthe application of'y which willv he indicated in the` following claims.

.In the: drawing; wherein I have shown severa embodiments" ofi .myzinventi'lin.l

7;' 'Figure-r isatop plan. view oranelectricalcone Space between. and at .2. ductor to the end of which is attached one form. of my electricaly connector;

Figure. 2 is a. section taken along line 2-.2

of. Figure 1';

Figure. 3 is a top` plan View of another form.

ofmy electrical .connector secured .to a conductor;

Figurev 4 isa sectiontakenalongthe lined-IL of. Figure 3; and,` l Figure 5 is a section similar to those shown. inFigures 2. and 4, of another form of` my con. nector.

Similar reference characters refer to similar parts. throughout the various views of= the. drawing.

Referring. first to Figure l, the connector. is, generally, indicatedatfland comprisesaferrule- Il., from one open. end, I2 ofv which extends av terminal connector I3, the other end Mci the connector also being. openin order. that the ferrule may receive the end. of a conductorV I5, preferably covered with insulation, I6.

As is. more. clearly shown inFigure2, the end.

of conductor I5. is preferably stripped of. itsinsulation. so that. the metal wire or the strands I] of. the conductor may be inserted Within. the ferrule Il. After insertion of the stripped conductor end within the ferrule, the ferrule is crimped, as at lli-2|., 19.-.22and 2li- 23 on op?,

posite sides, with suflicient force that the inner surfaces. I8a, 19a. and 20a, and 21a,A 22121,V and.` 23a of the crimps. arev squeezed against the opposite sides of ythe. strands of wire H with very sub stantial force. so as to pressV thev strandsy intol closeengagemcnt. Indeed, the crimping pressureis.l preferably such that the strands of wire. Il are pressedsubstantial-ly into ai solid piece which appears substantially freeY from crevices ifa cross)l section through the center of a crimpis cutv and; polished. Thus ra v goodelectrical contactbetween.

the ferrule and .theconductor^Wireis assured.

A- single. crimp would.'v be eiective in manycases toaccornplish thepurposes. of my invention.. If, however, spaced criinps Vare rstformed quite close together, and then. whilel these areheld compressed between the. crimping diesy the: areal therebetween is crimped, thei plastic is first extruded from, both sidesinto the. centralxspaceand thenA being compressed. ina connedspaca the plastic isrdrivenunder pressure into the-ineterstices andcrevices between. the crimpedA areas, thus assuringk aV perfect seal.

rst. extrudi'ns from. both A somewhatan-y alogous. effect is producedwhen .two closelyspacedl. crimps are formeel'. simultaneously.; the plasticV .sides into. the narrow.- IiaLstasez beng .cprn;-

s 3 pressed under very high pressure which drives it into every space and crevice.

A short distance either side of this central cross-section, however, the wire will be less severely compressed, and gradually crevices appear and open out to relatively large openings between the strands beyond the crimp. Except for the present invention, these crevices would make entries wherein corrosion could begin and Work its way in toward the crimp along the surfaces of the wire strands and of the ferrule. This corrosion I forestall by my present invention, completely excluding from a contact area all air. and moisture; accordingly I have disposed the plastic material 24 between the wire strands Il and the inside of ferrule II.

This material may be selected from the wide variety of plastic materials available which have the property of adhering to the metal contact surfaces and extruding under pressure and which do not corrode metals. As examples of these, I can use with advantage either straight or plas,- ticized raw rubber, polyisobutylene, ysynthetic rubbers, vinyl polymers, styrene polymers and acrylic type polymers; also cellulose derivatives such as cellulose nitrate, acetate butyr'ate and the like. These plastics ordinarily have excellent insulating qualities, but according to my present invention I take advantage oftheir plasticity to extrude them completely from the contact areas by the same pressure which forms the crimp.

The plastic used may be permanently plastic, or may be capable of conversion to a non-plastic material by heat or pressure or other special treatment; it should not, of course, becomenon'- plastic spontaneously under conditions of storage or handling prior to application onto a wire.

Elastomers may be used in the same manner in that a thin film applied tothe interior of theferrule is formed to the surface of the wire strands in the crimped area and the strands push through the lm into contact with the ferrule. In this case, however, the elastic properties of the film tend to crowd the lm into the crevices between the wires and ferrule, and maintain a perfect seal after the manner of the familiar rubber dam used in dental work.

` The conductor I is coated with the plastic or the inside of ferrule is lined with the plastic, or both. The ferrule may then by placed overy the end of the conductor and thereafter crimped. Upon crimping of the ferrule, the plastic iiows from between the strands offthe conductor and the ferrule at the bottoms of the crimps thus establishing electrical contact 'at` The plastic extruded from these points of contact is compacted in bordering zones,` thereby effectively precluding the passage 'of air' these points.

the interstices therebetween so as to seal com-'' pletely Vcontact areas within the ferrule.

Under certain circumstances, I have vfound it preferable also to insulate the outer periphery of ferrule II. Thus, I may apply to the outside of ferrule II a suitable insulation 25.which1re; sists extrusion-underpressure of the crimping die' and, upon the" vterru'les being" crimped, profv vides eiective insulation thereon. However, the outer insulation may comprise the same sort of plastic as used within the ferrule so as completely to insulate the inside and the outside, as well as the ends thereof. Under such circumstances, I have found it advantageous to dip the ferrule in the insulating plastic prior to its being placed over the stripped end of the conductor.

.Thus it may be seen that the insulating plastic 24 is effectively forced into and about the strands 'of conductor I5 and may even be forced between ferrule end I4, and the adjacent edge of insulation I6 on conductor I5. The insulating material lyingbetween the open end I2 of the ferrule and the wire strands I'I, seals otherwise exposed areas of the conductor.

As shown in Figure 3, another form of my connector is generally indicated at 3B and comprises a ferrule 3| having an open end 32, from which extends a terminal connection 33. From the other end of ferrule 3| extends a collar 34 or the like, through the outer end of which extends the end of insulated conductor I5. As shown in Figure 4, a portion Ia of the conductors insulation lies within ferrule collar 34, the stripped end or wire strands I'I of the conductor lying within the ferrule 3|. The ferrule collar 34 is crimped as at 36 against portion |6a of the conductor insulation, ferrule 3| being crimped, as in the case of tightly squeeze, adhere to and have good electrical contact with the wire strands I1. Disposed between the wire strands I'I and the ferrule is insulating material 31, this material also lying between collar 34 and portion |6a of the conductor insulation, and also between thelend 35 of the ferrule and the conductor insulation. The insulating material is extruded or forced into the.

so as to be in position and condition for extrusion.

into interstices around contact areas and about the wire strands when th-e ferrule is crimped.

thereon. While I have not shown an exterior coating of insulation on the ferrule of connector 30, it is to be understoodthat ferrule 3| may be provided with an outer coating of insulating plastic in the same manner as -that described in con,

nection with connector II)` (Figure 2).

Thus itsmay be seen that connector 3a is not only securely attached to conductor I5 so as to bein good electrical contact with wire strands.'

II, but also the end of the conductor can be effectively sealed against the admission into and flow therethrough of air and moisture.

In Figure 5, I Ahave shown connector I0 applied to a conductor 40 which is provided with 'a' plastic insulation of such a character that stripping of the conductor end is unnecessary priorto application or attachment thereto of connector same manner as the plasticv insulation 24, for example, described in connection with the connector shown inl Figure 2. Thus the plastic isforcedl into sealing rings v4| .or the like, between adjacent crimps,I 'andalso into any interstices bel'liv'een4 adjacent ,wirestrands I'I, effectively .to preclude the'flow'of air and moisture therethrough. 'While I have not shown the outside of ferrule l i in Figure 5 insulated exteriorly, it will be understood that this ferrule may have an outer insulation as in the case of that shown in Figure 2.

Accordingly it will be seen that I have provided an electrical connector for solderless attachment to a conductor end, and a method of attaching the connector thereto, which attains the several objects set forth hereinabove in a thoroughly practical and efficient manner.

Many possible embodiments may be made of the mechanical features of the abo-ve invention, and the art herein described might be varied in various parts, all without departing from the scope of the invention.

I claim:

1. The method of attaching a metallic ferrule to an electrical conductor which includes the steps of, dipping said ferrule into a liquefied plastic insulating material so as to insulate it inside and out, solidifying the plastic, disposing said conductor within said ferrule, and exerting substantial pressure on said ferrule transversely thereof at spaced portions therealong to force said ferrule into good electrical contact with said conductor end and squeezing the plastic material within said ferrule along said conducto-r into localized areas between said pressed portions of the ierrule.

2. The method of attaching a metallic ferrule to an electrical conductor, which includes the steps of, applying a plastic insulating material on at least one oi the contacting surfaces of said ferrule and said conductor, inserting said conductor in said ferrule, exerting substantial transverse pressure on said ferrule at longitudinally spaced portions thereof to force said ferrule portions into good electrical contact with said conductor thereby forcing said plastic insulating material into a compact mass between said spaced portions of the ferrule, and while maintaining said pressure at said spaced portions of said ferrule, exerting transverse pressure on said ferrule between said spaced portions to force said plastic material into all interstices within said ferrule between said first-mentioned spaced portions.

3. An electrical connector having an openended ferrule and a lining of solid insulating material on at least the inside of the ferrule, the insulating material having a resistance to cold pressure flow less than that of the metal of the ferrule.

4. In an electrical connection, an electrical conductor, and a sleeve-like connector ferrule telescoped over the conductor; the conductor being in good electrical contact at a plurality of points with the inside of the ferrule, and a corrosion-resistant plastic barrier on the inside of the ferrule surrounding and sealing the individual points of electrical contact therebetween against the atmosphere.

5. An electrical connector including a metallic ferrule having a wire-receiving portion therein;

said ferrule being covered inside and out with a solid insulating material, insulating material on the outside of the ferrule being harder than that on the interior of the ferrule and having a resistance to cold pressure ilow not signicantly less than that of the metal oi the errule.

6. The method oi providing an electrical connector on the end of an electrical conductor which includes the steps of: providing an electrical connector ferrule having metal contact portions therein, providing an electrical conductor having metal contact portions thereon, applying to the contact portions of one of the electrical members a coating of a malleable plastic insulating material, putting the ferrule over contact portions of the conductor, and pressing fer rule contact portions against conductor contact portions in a plurality of axially spaced areas with such force as to cause plastic film. flow and the establishment of opposing contact portions in good conducting relationship.

7. The method of making an electrical connection which includes the steps of: providing a metallic connector ferrule having a wire-receiving portion therein, insulating the inside of the fer-rule with plastic insulating material which is solid, but softer than the metal of the errule when crimped at room temperature, inserting electrical conductor strands into the thus insulated wire-receiving portion of the ferrule, and crimping the ferrule onto the strands with sufficient pressure to penetrate said insulation at a substantially line or point contact to cause a cold metal flow in the ferrule and conductor strands.

FRANK J. SSWA.

file of this patent:

UNTED STATES PATE-NTSy Number Name Date 762,840 Osborn June 14, 1904 1,096,699 Elkin May 12, 1914 1,227,726 Woodhead May 29, 1917 1,706,005 Thompson Mar. 19, 1929 1,827,297 Moore Oct. 13, 1931 1,975,885 Wellman Oct. 9, 1934 2,226,849 Douglas Dec. 31, 1940 2,251,176 Temple, Jr. July 29, 1941 2,280,352 Penfold Apr. 21, 1942 2,379,567 Buchanan July 3, 1945 2,385,792 Carlson Oct. 2, 1945 2,423,290 Bonwitt July l, 1947 2,437,220 Bonwitt Mar. 2, 1948 FOREIGN PATENTS Number Country Date 525,597 England of 1940l 290,696 England May 17, 1928 

